Singlet oxygen photogeneration and 2,4,6-TCP photodegradation at Pt/TiO2 under visible light illumination

Abstract

Pure and Pt nanoparticle-modified rutile TiO₂ were synthesized via hydrolysis of TiCl₄ in the absence or presence of Pt nanoparticles. HRTEM, XRD, and SEM were used to characterize the structure of the prepared catalysts. The resulting modified TiO₂ catalysts show extended visible light absorbance. Photodegradation of 2,4,6-trichlorophenol (2,4,6-TCP) over these photocatalysts was investigated under visible light illumination. The Pt nanoparticles facilitate the separation of photogenerated electron–hole pairs at low Pt content, then enhances the photodegradation rate of 2,4,6-TCP. 0.18Pt–TiO₂ achieved the best photocatalytic activity among the tested catalysts. It was found that singlet oxygen rather than ˙OH acts as the main oxidative species for the degradation of 2,4,6-TCP according to the experimental results. The degradation intermediates of 2,4,6-TCP were identified and the degradation pathway was proposed. Pt nanoparticles on TiO₂ significantly enhance O₂ adsorption and the formation of ˙O₂ ⁻. The rutile surface is a favorable condition for stabilizing ˙O₂ ⁻. These properties of the Pt nanoparticle-modified rutile TiO₂ facilitate the formation of ¹O₂via the reaction of superoxide anions with holes.